try to figure out this gas gauge problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

gabet40 · 08-19-2002, 09:58 PM

my needle always stays at 3 o'clock until my gas tank gets low. then when i accelerate OR if my truck is inclined the needle starts going towards empty to let me know that im low. then when i stay at a constant speed, slow down, or level the truck out, itll go right back to 3 o'clock.
so it seems that when im low and the fuel is shifting towards the back of the tank, it starts working. any ideas?

*Zkast* · 08-19-2002, 10:29 PM

Unless you have a wire loosing connection (doubtful) It sounds like you have a bad sending unit in the tank. When the gauge goes past full thats an indication of a broken wire, or open in the sending unit assembly.

Slammed67 · 08-19-2002, 11:10 PM

I just hooked up the wire to my fuel cell sending unit and when I turned on the key, it went to the 3 o'clock position also. Just out of curiosity, I ran a ground wire from the sending unit housing to the frame (thus grounding it) and it worked fine. However, assuming you have the stock gas tank, grounding shouldn't be an issue since there is so much metal to contact by the way the tank is mounted. So, whatever that is worth to ya! Good luck.

Blazer1970 · 08-20-2002, 07:46 AM

I agree, bad sending unit. What does it do when the tank gets really low?

**GMCPaul** · 08-20-2002, 07:55 AM

Sounds as though the resistor that the fuel sending unit arm pivots up and down on in tank is broken at the bottom of where it connects inside the small housing on the sender and when tank is low on fuel and you accelerate or decelerate it allows the piece on arm to contact the resistor strip.
GMCPaul

gabet40 · 08-20-2002, 01:34 PM

i like pauls idea. its a blazer tank and the sending unit never worked from when i first put it in. funny thing is that it had problems when i had the stock tank in as well. maybe two bad sending unit huh.
slammed 67- it isnt a stock tank but the ground is on the frame. ill double check i have em right though
blazer1970- when it gets really low, the guage will actually stay at empty, then when i throttle more than about 30% my engine will start gasping. thats really low
but ive been planning on pulling it down and readjusting the straps cuz its really low right now so ill let you guys now what i come up with

*Fast68Chevy* · 08-20-2002, 02:17 PM

keep in mind that fuel guage is fed hot feed at all times when ingition is on, the tan wire that runs back to the tank sender is a variable ground, the sender is grounded to the tank that is grounded ot the truck and the ground all passes through the resistor winding strip on the sending unit assembly, and the arm has a contact on it that glides along the length of the reistor strip and that lessens or greatens ground feed to the gauge, IE moving the needle

if you break(opne the circuit) then the guage will peg over to the right, around 3 o clock,.

problem can be wire, contact somewhere or the sender unit,
most commonly damaged wire and/pr bad unit,

08-19-2002, 09:58 PM	#1
gabet40 Registered User Join Date: Dec 1999 Location: Modesto, CA Posts: 565	try to figure out this gas gauge problem my needle always stays at 3 o'clock until my gas tank gets low. then when i accelerate OR if my truck is inclined the needle starts going towards empty to let me know that im low. then when i stay at a constant speed, slow down, or level the truck out, itll go right back to 3 o'clock. so it seems that when im low and the fuel is shifting towards the back of the tank, it starts working. any ideas? __________________ Current owner of 2016 2500 Silverado Midnight Edition. Former owner of: 69 1/2 ton, change from long/fleet to short/fleet, shaved door handles, shaved tailgate, 4/6 drop, power windows, 700r4 72 blazer, 350 with Holley Commander 950 DFI, crane energizer cam, 350 tranny, dual sanderson blockhuggers/magnaflow exhaust

08-19-2002, 11:10 PM	#3
Slammed67 Progress = 0% Join Date: Nov 2001 Location: Kansas City, MO Posts: 2,108	I just hooked up the wire to my fuel cell sending unit and when I turned on the key, it went to the 3 o'clock position also. Just out of curiosity, I ran a ground wire from the sending unit housing to the frame (thus grounding it) and it worked fine. However, assuming you have the stock gas tank, grounding shouldn't be an issue since there is so much metal to contact by the way the tank is mounted. So, whatever that is worth to ya! Good luck. __________________ Jason - '67 GMC swb \| '57 Bel-Air 4dr hardtop \| '56 210 4dr Wagon \| 2000 GMC Sierra

08-20-2002, 07:46 AM	#4
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	I agree, bad sending unit. What does it do when the tank gets really low? __________________ Tim

08-20-2002, 07:55 AM	#5
GMCPaul Senior Member Join Date: Mar 2000 Location: Rockville,In. USA Posts: 3,721	Sounds as though the resistor that the fuel sending unit arm pivots up and down on in tank is broken at the bottom of where it connects inside the small housing on the sender and when tank is low on fuel and you accelerate or decelerate it allows the piece on arm to contact the resistor strip. GMCPaul __________________ Secure Online Catalog for-GMCPauls Truck Parts Email- GMCPAULS@GMAIL.COM

08-20-2002, 01:34 PM	#6
gabet40 Registered User Join Date: Dec 1999 Location: Modesto, CA Posts: 565	i like pauls idea. its a blazer tank and the sending unit never worked from when i first put it in. funny thing is that it had problems when i had the stock tank in as well. maybe two bad sending unit huh. slammed 67- it isnt a stock tank but the ground is on the frame. ill double check i have em right though blazer1970- when it gets really low, the guage will actually stay at empty, then when i throttle more than about 30% my engine will start gasping. thats really low but ive been planning on pulling it down and readjusting the straps cuz its really low right now so ill let you guys now what i come up with __________________ Current owner of 2016 2500 Silverado Midnight Edition. Former owner of: 69 1/2 ton, change from long/fleet to short/fleet, shaved door handles, shaved tailgate, 4/6 drop, power windows, 700r4 72 blazer, 350 with Holley Commander 950 DFI, crane energizer cam, 350 tranny, dual sanderson blockhuggers/magnaflow exhaust

08-19-2002, 10:29 PM	#2
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	Unless you have a wire loosing connection (doubtful) It sounds like you have a bad sending unit in the tank. When the gauge goes past full thats an indication of a broken wire, or open in the sending unit assembly.

08-20-2002, 02:17 PM	#7
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	keep in mind that fuel guage is fed hot feed at all times when ingition is on, the tan wire that runs back to the tank sender is a variable ground, the sender is grounded to the tank that is grounded ot the truck and the ground all passes through the resistor winding strip on the sending unit assembly, and the arm has a contact on it that glides along the length of the reistor strip and that lessens or greatens ground feed to the gauge, IE moving the needle if you break(opne the circuit) then the guage will peg over to the right, around 3 o clock,. problem can be wire, contact somewhere or the sender unit, most commonly damaged wire and/pr bad unit,



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